Nguyen Tuan Hung created AVRO-3220:
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Summary: How Many Decibels Are My Headphones?
Key: AVRO-3220
URL: https://issues.apache.org/jira/browse/AVRO-3220
Project: Apache Avro
Issue Type: New Feature
Components: build
Affects Versions: 1.7.2
Environment: I'm assuming you're checking the decibel levels of the
music you're listening to with headphones to see if they're safe to listen to
while driving or exercising. Also, I'm assuming these headphones have
over-the-ear earcups. I'll modify my response to fit these criteria, but the
setup described below can be used with minor modifications for other types of
headphones and tests. Headphones that fit over the ear will require no
adjustments. Anything that holds earbuds will have to be similar in shape to an
enclosed ear canal.
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Frequency response measurements can also be performed with this set-up, but the
accuracy degrades quickly. In other words, the more realistic your model looks
in your head, the more accurate your measurements will be.
To make binaural recordings, you'll need to buy a dummy head and mount a
microphone in each ear afterwards. These are the most realistic spatial
recodings you'll hear through headphones if you do this. However, let's return
to the dB meter.
A dB meter is first and foremost required. These can be purchased for less than
$50 on the internet or at a music or electronic supply store. They are also
readily available. If there's a Radio Shack near you, they have a wide range of
models. You can use your smartphone if this is a one-time measurement. There
are numerous free dB metering apps to choose from. It's fine to use an app if
you're just curious and don't need a lot of precision. Read reviews before
ordering a meter online to avoid purchasing a dud.
If you're unsure about the accuracy of a dB app, test it out with some familiar
sounds. A library, traffic, and conversations all have dB levels that are
easily found on the internet. To get an idea of how loud a room is, take the
decibel level and divide it by the number of people present. Anything that
exceeds a decibel level of 140 will cause immediate harm. When exposed for an
extended period of time, lower levels can do you harm. After about 10 seconds
of exposure to 120dB, your ears will be damaged. After about 10 minutes, the
noise level of 100 decibels becomes harmful. Keep your ears to yourself. As
long as you limit your exposure to loud noises, you'll be able to use
headphones and have enjoyable conversations for years to come.
Use a meter or app that is "C" weighted, regardless of what you use. A and C
are the most commonly used dB metering weightings. Other weightings exist, but
they're reserved for specialized applications, so you won't see them very
often. "A" weighting, in my opinion, is ineffective because it only includes
roughly the speech frequencies, severely excluding the low ones. It's used for
determining whether or not a product meets federal safety standards for noise
emissions. Other than covering your butt legally, I don't see any real-world
application for it. Extremely loud sounds, regardless of frequency, are harmful
to the ears. You should include all the audible frequencies in your measurement
of how loud a sound is, not just the middle ones, if you want a reference
measurement from headphones. The weighting "C" is the other alternative. The
frequency range covered by C is extremely broad. All measurements should be
done with a C weighting.
You'll also require something cheap to place the headphones against so that you
can record all of the sound output and use that for your analysis. It has to be
larger than the earcups on your headphones in terms of both size and shape. If
you want to go all out, a stryrofoam dummy head from a craft store like
Michaels costs less than $10. You could use a styrofoam ball that's the same
size and shape, but you'll have to flatten the ear area to make it fit your
head. If your earcups fit snugly on it, a styrofoam board will do.
To use a styrofoam board, simply place the earcup on top of the board and press
down. Your phone or meter's microphone end should fit snugly through a small
cutout in the board so that you can accurately measure the distance. Fill in
any gaps around your meter or phone with scraps from your cutting project.
Don't bury the display if you want to be able to read the results from the
other side. Again, the most important thing to remember is to keep the area
around the meter or phone as quiet as possible to avoid having inaccurate
readings. When you wear headphones, sound is contained within a small enclosure
on your head. When you put on headphones while wearing sunglasses, the sound
will be muffled.
The Styrofoam board must be thick enough to prevent vibration and sound energy
transmission away from your measurement. If you use thicker stryofoam, you can
keep your meter or phone's microphone end from sticking through the cutout hole
and away from the speaker in the headphone earcup so that you don't damage the
speaker. In order to avoid frequency irregularities that may be picked up from
different spots on the speaker's surface if the microphone is too close, it may
be beneficial to keep some distance between the microphone and the speaker.
Styrofoam is a good material for your test set up because it absorbs little
sound and can be easily cut. If you'd rather use wood, plastic, or heavy
cardboard, those materials will work as well. Avoid using anything that absorbs
sound, such as cloth. A lot of the styrofoam from packaging cartons can be used
instead of being thrown away. The idea is to give the earcups a head-like, or
at the very least flat, shape so that no sound escapes. Here's where you have
room to express yourself.
Cut a hole in the ear canal area and a meter cutout on the side of a dummy head
if you're looking for utmost accuracy. As long as the dB meter does not
interfere with the earcups, you can place it on any convenient side. Any air
gaps around the dB meter or the earpads should be sealed off to prevent sound
from leaking into the room. It isn't possible to duplicate the sound path to
your eardrum because your ear canal doesn't have any such gaps. That's all
there is to it.
As soon as your cutout is partially in, make sure you can read the meter or
phone display. Instead of inserting the entire meter, just the microphone
portion will go in. The rest of the meter will remain out in the open. If your
touchscreen or buttons aren't touching, you'll want to exercise caution when
using the phone.
Make sure you're listening to music at a volume you're comfortable with before
you begin. Then, without touching the volume controls on your headphones,
remove them from your head and set them on your test head or test plate. Take a
look at what you've read!
Reporter: Nguyen Tuan Hung
Fix For: 1.10.2
h1. How Many Decibels Are My Headphones?
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